The present invention is related to a machining machine having at least one upper machining disc with annular machining plane, which is rotatingly drivable around a vertical axis. A lower machining plane is assigned to the upper machining plane, which is either stationary or mounted on a lower machining disc. Between the machining planes, a machining gap is formed, in which rotor discs are arranged, which accommodate workpieces in recesses. On their part, the rotor discs are brought into a rotational movement with the aid of a rolling device, with the aid of pin- or tooth rings for instance, so that they move on a cycloid path with the workpieces. Machining machines with upper and lower machining disc are called double side machines. With the same, a plane-parallel machining of the workpieces is performed, of semiconductor discs (wafers) for instance. The machining may consist of grinding, lapping, polishing or the like. Depending on the machining process, the machining planes have machining coatings which engage with the workpiece planes. Depending on the machining process, a tapping fluid is introduced into the machining gap, which optionally contains polishing or lapping material, respectively.
In DE 103 44 602 A1 for instance, a grinding method according to the so-called “floating processing” is disclosed in order to perform an abrasion of material rapidly and in a cost-saving manner. In this method, the workpieces are accommodated relatively loosely in the recesses of the rotor discs.
The geometry of the machining gap is decisive for the precision of the workpieces, i.e. their absolute evenness and parallelism. It is crucial that the machining gap is formed by parallel machining planes which are as parallel as possible. However, it has been proven that thermal expansion effects influence the machining gap and lead to an undesired workpiece geometry. The deformation of the machining discs during the grinding process is due to a bimetal effect, in which regions of the machining disc are warmed up differently.
From DE 10 2004 040 429, it is known to use this bimetal effect to deform the machining disc by influencing the temperature of a carrier disc for the machining disc, namely depending on the temperature of the machining disc. The latter is deformed such that the machining plane gets a certain contour in order to achieve a largely parallel machining gap.
In machining discs which have, without intermediate element, a machining coating which is abraded with increasing usage, it becomes necessary to replace the machining disc or to apply a new machining coating, when the same has been abraded for a certain amount.
For the condition of the machining gap or its control, respectively, the temperature in the machining gap is decisive. From the document cited above, it is already known to measure the temperature of the machining disc or in the machining gap, respectively, besides to the distance of the machining discs.
The upper machining disc is pressed against the lower machining disc with a preset pressure. The pressure is not inessential for the temperature and the degree of abrasion in the course of time. In known machining machines, a preset pressure can be applied to the machining disc without that it is known how great the pressure per unit area of the plane to be machined of the workpieces is.